C-band cross-coupled SIW filter using a novel topology of electric coupling

This paper presents a novel technique of cross-coupling based on a thick film microstrip line. This cross-coupling, which is introduced between non adjacent resonators on a folded version of a substrate integrated filter (SIW), allows the creation of finite transmission zeros aimed at increasing rejection. This technique was applied to a C band 6th-order inductive post SIW filter. Its performances are compared to those of another filter based on a cross-coupling through a classical coplanar line. Both filters proved to be compatible with planar technology through use of specific transitions. All filters were realized on a standard ceramic substrate (h = 380 μm, εr = 9.9, tanδ = 0.0003). Experimental results are in agreement with those from simulations.